The ticker symbol for the Chicago Board Options Exchange (CBOE) Volatility Index, which shows the market's expectation of 30-day volatility. It is constructed using the implied volatilities of a wide range of S&P 500 index options. This volatility is meant to be forward looking and is calculated from both calls and puts. The VIX is a widely used measure of market risk and is often referred to as the "investor fear gauge".

There are three variations of volatility indexes: the VIX tracks the S&P 500, the VXN tracks the Nasdaq 100 and the VXD tracks the Dow Jones Industrial Average.

The first VIX, introduced by the CBOE in 1993, was a weighted measure of the implied volatility of eight S&P 100 at-the-money put and call options. Ten years later, it expanded to use options based on a broader index, the S&P 500, which allows for a more accurate view of investors' expectations on future market volatility. VIX values greater than 30 are generally associated with a large amount of volatility as a result of investor fear or uncertainty, while values below 20 generally correspond to less stressful, even complacent, times in the markets.